1. Field of the Invention
This invention is directed to an extremely sensitive method for detecting the presence of a liquid metal fluid, primarily for use in liquid metal cooled nuclear reactors. More specifically, liquid metal vapor in an air sample is allowed to react with a radioactively tagged substance, whereby a radioactive gas is released in proportion to the amount of metal fluid and is monitored.
2. Description of the prior art
In all nuclear reactors, detection of leakage of reactor coolant from the primary system is of maximum importance to safe operation of the reactor facility. The earlier detection occurs, the less likely there will be detrimental effects to the reactor systems, to operating personnel, and to the environment. A detection system which can detect leaks of a small magnitude further insures that such small leaks will not be allowed to propagate.
The reactor primary system is typically enclosed in a large containment structure, and the atmosphere within the containment is controlled to minimize environmental releases. A containment structure is roughly 150 feet in diameter, and over 200 feet high, containing an internal free volume on the order of three million cubic feet. Small leaks of reactor coolant, therefore, are greatly diluted and require an extremely sensitive detection system. Some reactors use a liquid metal coolant, such as sodium, potassium, or a combination of the two ("NAK"). A primary system leak in such reactors will release such liquid metal as a vapor due to the high operating temperature of the reactor. This invention provides an extremely sensitive method for detection of the liquid metal, such as sodium, or "NAK," released as a vapor.